Experimental assessment of wind erosion after soil stabilization treatments at Eneabba,Western Australia

Wind tunnel experiments on rehabilitation surfaces at Eneabba, Western Australia evaluated the techniques used by Associated Minerals Consolidated Ltd. (AMC) and Allied Eneabba Ltd. (AEL) to stabilize regions being revegetated following heavy mineral sand mining. Newly landscaped areas proved to be the most erodible, beginning to erode at 9 m sec⁻¹ and producing a soil flux of 10 kg m⁻¹ min⁻¹ at 18 m sec⁻¹ wind speeds. Sandier, more organically-rich, surfaces in the rehabilitation areas were somewhat less erodible with losses of only 2 kg m⁻¹ min⁻¹ at wind speeds of 18 m sec⁻¹. The mining companies use various nurse crops and top dressing mulch for surface stabilization. Rows of oats, sparse plantings of the grass cultivar “SUDAX” (Dekalb ST6) supplied by Westfarmers Ltd. and applications of Terolas, a cold, bituminous surface binding material supplied by Shell Co. of Australia Ltd., all proved successful in reducing wind erosion in this semi-arid region where more than 25% of summer days experience winds greater than 8 m sec⁻¹.     

Mammalian breath: trigger of defensive chemical response in a tenebrionid beetle (Bolitotherus cornutus)

Summary The tenebrionid beetle Bolitotherus cornutus everts a pair of quinone-producing defensive glands in response to mammalian breath. Experiments with a controlled airstream indicate that the beetle recognizes breath on the basis of temperature, humidity, and airflow dynamics. Under attack by mice the beetle everts the glands immediately upon being mouthed and may secure its release as a result. Against ants the beetle is protected by its tough exoskeleton and usually refrains from everting the glands. Other arthropods also show defensive responses when breathed upon.Paper No. 77 of the series Defense Mechanisms of Arthropods     

Multi-year, seasonal genotypic surveys of coral-algal symbioses reveal prevalent stability or post-bleaching reversion

This report documents the extent to which coral colonies show fluctuations in their associations with different endosymbiotic dinoflagellates. The genetic identity of Symbiodinium from six coral species [Acropora palmata (Lamarck), A. cervicornis (Lamarck), Siderastrea siderea (Ellis and Solander), Montastrea faveolata (Ellis and Solander), M. annularis (Ellis and Solander), and M. franksi (Gregory)] was examined seasonally over five years (1998 and 2000–2004) in the Bahamas and Florida Keys at shallow (1 to 4 m) fore-reef/patch reef sites and at deeper fore-reef (12–15 m) locations. Symbionts were identified genetically using denaturing gradient gel electrophoresis (DGGE) fingerprinting of the internal transcribed spacer region 2 (ITS2) of ribosomal RNA gene loci. Repetitive sampling from most labeled colonies from the Bahamas and the Florida Keys showed little to no change in their dominant symbiont. In contrast, certain colonies of M. annularis and M. franksi from the Florida Keys exhibited shifts in their associations attributed to recovery from the stresses of the 1997–1998 El Niño southern oscillation (ENSO) event. Over several years, a putatively stress-tolerant clade D type of Symbiodinium was progressively replaced in these colonies by symbionts typically found in M. annularis and M. franksi in Florida and at other Caribbean locations. Greater environmental fluctuations in Florida may explain the observed changes among some of the symbioses. Furthermore, symbiotic associations were more heterogeneous at shallow sites, relative to deep sites. The exposure to greater environmental variability near the surface may explain the higher symbiont diversity found within and between host colonies.     

Does information of predators influence general wariness?

Antipredator behavior includes several qualitatively distinct activities, but few studies have determined the degree to which these activities are independent. If behaviors are not independent, then the nature of the relationship would illustrate potential performance constraints. We studied crimson rosellas (Platycercus elegans) and first focused on acoustic predator discrimination. We measured time allocation before and after playback of one of three experimental treatments (peregrine falcons—Falco peregrinus, wedge-tailed eagles—Aquila audax, and crimson rosellas) to determine whether or not rosellas discriminated predators from non-predators, and specifically whether or not they discriminated large from small predators. We then focused on the decision to flee. We experimentally approached subjects and measured the distance at which they oriented to us (alert distance) and the distance at which they fled (flight initiation distance; FID). We found that rosellas could distinguish among predators; however, there was no effect on general wariness as measured by FID. These two processes of antipredator behavior may, thus, be independent.     

Pitch shifts and song structure indicate male quality in the dawn chorus of black-capped chickadees

The fee-bee song of male black-capped chickadees (Poecile atricapillus) is considered a single-type song that singers transpose up and down a continuous frequency range. While the ability to shift song pitch in this species provides a mechanism for song matching as an aversive signal in male-male territorial song contests, the functional significance of this behaviour during the solo performances of males during the dawn chorus is unclear. We analysed the dawn chorus songs and singing behaviour of males whose winter-flock dominance status we determined. We used correlation analysis to show that pitch shifts were accompanied by changes to other fine structural characteristics in song, including temporal and relative amplitude parameters. We also found that songs of socially dominant males and songs of their most subordinate flockmates could be distinguished using these methods by the way they performed a between-note frequency measure accompanying pitch shifts. That is, a ratio measure of the internote frequency interval remained constant for songs of high-ranking birds despite changes in absolute pitch, while low-ranking males sang a smaller ratio as they shifted to higher absolute pitches. These findings identify previously unrecognised variation in the songs of black-capped chickadees. More importantly, they indicate a mechanism by which pitch shifting during the dawn chorus of black-capped chickadees could provide a reliable indicator of relative male quality.Communicated by I. Hartley     

Juvenile–adult associations in sea urchins ( Strongylocentrotus franciscanus and S. droebachiensis ): protection from predation and hydrodynamics in S. franciscanus

Juvenile red sea urchins, Strongylocentrotus franciscanus, aggregate under adult conspecifics, whereas sympatric juvenile green sea urchins, Strongylocentrotus droebachiensis, are typically more solitary and dispersed. Neither the potential advantage of juvenile sheltering nor the differences in post-settlement behavior between the two species has been demonstrated experimentally, but may be related to protection from predators and/or hydrodynamics. In predation experiments, juvenile vulnerability differed in the two species as the seastar Pycnopodia helianthoides consistently chose juvenile S. franciscanus over S. droebachiensis (100% vs. 0%). When associated with adults, juvenile mortality decreased dramatically in S. franciscanus (90% alone vs. 5% with adults), but very little in S. droebachiensis (85% vs. 75%). Not surprisingly, juvenile behavioral responses in the two species reflect this difference in vulnerability. Juvenile S. franciscanus sheltered under adults when predation risk was high, but not when risk was low (44% vs. 13%), whereas sheltering in S. droebachiensis was infrequent and not related to predation risk (7% for high risk versus 5% for low risk). From a hydrodynamic perspective, the presence of an adult led to the creation of a hydrodynamic refuge for juveniles, where average water velocities were reduced by > 60% around the adult urchin. Again, striking differences in sheltering rate were apparent in S. franciscanus (52% vs. 13% for high flow and low flow, respectively), but not S. droebachiensis (5% for high flow versus 4% for low flow). Sheltering behavior was also species-specific as juveniles did not shelter at high rates under adults of the opposite species (≤ 16%). A field survey confirmed these finding in that juvenile S. franciscanus abundance was associated with both adults and water motion (R ² = 0.80, P = 0.008, best-subsets regression). These results suggest that sheltering confers juvenile S. franciscanus with a degree of protection from predators and water motion, and that species-specific differences in this post-settlement behavior may be related to the differences in the protection afforded by adults.     

Aggregation and foraging behavior of whirligig beetles (Gyrinidae)

Summary Whirligig beetles aggregate in the daytime into dense single-and multispecies groups (rafts) of hundreds or thousands of individuals. On the 22km shoreline of Lake Itasca in northern Minnesota, these aggregations were on the average 0.8 km apart, and they were usually found day after day in the same ocations.Most beetles apparently do not home to the aggregation of their origin after dispersing at night because (a) the species composition of some aggregations changed greatly, and (b) paint-marked beetles (Dineutus horni) moved overnight from one aggregation as far as 4km, joining 11 of the 14 large (>300 beetles) D. horni groups on the lake.Throughout the night, the largest concentrations of beetles remained within 100m of the diurnal aggregation sites. Beetles reconvened into the compact rafts before daybreak, in part by following each other in sometimes long single files or trains. Their forward motion stopped after they joined large number of other beetles. We infer that following behavior enables those individuals that have dispersed from their original aggregations (during their nocturnal foraging) to find and join other aggregations before daylight.Naive fish ate the beetles despite their noxious secretions. However, fish living near rafting sites and feeding on insects on the water surface in daylight should soon learn to avoid the beetles. The rafting sites would then become safe places. We observed fish attacking only those beetles that had been either dispersed from their rafts or released into open water away from raft sites in the daytime. We speculate that the evolutionary significance of the aggregation behavior is related to predator (fish) avoidance.     

Suburban Areas in Developing Countries and Their Relationship to Groundwater Pollution: A Case Study of Mar del Plata, Argentina

2 were sampled in order to verify the impact of these problems on groundwater. All samples were analyzed for major ions, and about 30 of them for fecal coliforms and heavy metals. Nineteen samples were selected for pesticide analyses. The average nitrate content was 80 mg/liter, eight times the regional background value. Fecal coliforms were detected in 60% of the analyzed samples. Zinc content and a high Cl⁻/HCO₃ ⁻ ratio were observed in the surroundings of the solid waste disposal area. Moreover, lindane and heptachlor pesticides were detected in ten samples.     

ANALYSIS OF NITROGEN MANAGEMENT STRATEGIES USING EPIC1

ABSTRACT: This paper illustrates a method of using a hydrologic/water quality model to analyze alternative management practices and recommend best management practices (BMPs) to reduce nitrate-nitrogen (NO₃^--N) leaching losses. The study area for this research is Tipton, an agriculturally intensive area in southwest Oklahoma. We used Erosion Productivity Impact Calculator (EPIC), a field-scale hydrologic/water quality model, to analyze alternative agricultural management practices. The model was first validated using observed data from a cotton demonstration experiment conducted in the Tipton area. Following that, EPIC was used to simulate fertilizer response curves for cotton and wheat crops under irrigated and dryland conditions. From the fertilizer response functions (N-uptake and N-leaching), we established an optimum fertilizer application rate for each crop. Individual crop performances were then simulated at optimum fertilizer application rates and crop rotations for the Tipton area, which were selected based on three criteria: (a) minimum amount of NO₃^--N leached, (b) minimum concentration of NO₃^--N leached, and (c) maximum utilization of NO₃^--M. Further we illustrate that by considering residual N from alfalfa as a credit to the following crop and crediting NO₃^--N present in the irrigation water, it is possible to reduce further NO₃^--N loss without affecting crop yield.     

COMPARING SAMPLING SCHEMES FOR MONITORING POLLUTANT EXPORT FROM A DAIRY PASTURE1

ABSTRACT: Dairy cow pastures and feeding areas around barns can be a significant source of nonpoint source pollutants to nearby streams. To help document the significance of these sources, nutrient export in streamfiow from a 56.7-ha, mostly agricultural, watershed located in southwestern North Carolina was monitored from August 1994 to January 1996. Total nitrogen and phosphorus export rates from the upper, predominantly pasture, part of the watershed were 18.0 and 1.4 kg/ha/yr, respectively, as measured by weekly grab sampling and 18.7 and 4.9 kg/halyr, respectively, as measured from storm event monitoring. Nitrogen and phosphorus export rates for the area between the monitoring sites, which included overgrazed cow holding and feeding areas and farm buildings, were 376 and 86 kgfhalyr, respectively, for grab sampling and 351 and 160 kg/ha/yr, respectively, for storm event monitoring. To estimate the amount of reduction from nonpoint source controls necessary to effect a significant reduction in pollutant loading, statistical analyses of the load data were conducted. The analyses for the five pollutants monitored showed that total suspended solids would require the greatest reduction (34.6 percent for weekly grab and 33.6 percent for storm) in loading after the implementation of controls for statistical significance. Nitrate plus nitrite was found to require the least reduction (12.6 percent for weekly grab). Pollutant export rates computed from weekly grab samples and storm event samples used separately were compared to corresponding export rates computed from combining grab and storm event samples to assess the differences in monitoring schemes.